Current epidemiologic research on the health effects of environmental toxins is limited by the lack of refined estimates of exposure. The goal of this research is to improve the characterization and estimation of exposure to toxins which may cause non-malignant respiratory disease. Animal bioassays can provide information on the mechanisms of cellular responses to particular toxins. Results from bioassay will be translated into biologically plausible functions of lifetime exposure histories. Specifically, data on latency, thresholds of response, and sensitization of the host will be reflected in the construction of refined exposure estimates. The exposure parameters developed from bioassay data will then be tested in exposure-responsive models and compared to the more conventional estimates, for example, cumulative exposure, duration of exposure, and average intensity. Data will be used from several cohorts occupationally exposed to various pulmonary toxins. The initial work will use data from approximately 700 beryllium refinery workers who have been studied for health effects every three years since 1977. Additional analyses will use data from an ongoing study of approximately 2,300 auto workers exposed to machining fluids.